apache, apr: fix atomic handling

Since the apache package was introduced,
--enable-nonportable-atomics=yes was passed when
BR2_ARCH_HAS_ATOMICS. However, Apache doesn't take this option: it
only passes it down when building the APR library. But since we're
building APR separately, this statement had no effect.

So this commit removes the useless code from the Apache package, and
instead adds the appropriate logic to the apr package, using the new
BR2_TOOLCHAIN_HAS_SYNC_x symbols rather than BR2_ARCH_HAS_ATOMICS.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Bernd Kuhls <bernd.kuhls@t-online.de>